Filtering by relation count in SQLAlchemy

14
votes

I'm using the SQLAlchemy Python ORM in a Pylons project. I have a class "Project" which has a one to many relationship with another class "Entry". I want to do a query in SQLAlchemy that gives me all of the projects which have one or more entries associated with them. At the moment I'm doing:

[project for project in Session.query(Project) if len(project.entries)>0]

which I know isn't ideal, but I can't figure out how to do a filter that does what I require (e.g. Session.query(Project).filter(Project.entries.exists())).

Any ideas?

1
pythonsqldatabasesqlalchemypylons

1 Answers

21
votes

Session.query(Project).filter(Project.entries.any()) should work.

Edited credit of James Brady's comment, be sure to give him some love.